With the recent trend that electronic devices become compact and lightweight, a battery acting as a power source is also required to become compact and lightweight. As a battery which becomes compact and lightweight and capable of being charged and discharged at a high capacity, a lithium secondary battery is put into practical use, and is used for a mobile electronic device such as a small video camera, a mobile telephone, and a laptop computer, a communication device, and the like.
The lithium secondary battery is an energy storage device having high energy and power, and has an advantage in that the capacity or operating voltage is higher than that of other batteries. However, the lithium secondary battery has a problem in safety of the battery due to the high energy, and thus has a danger such as an explosion or a fire. In particular, since hybrid automobiles which have been recently in the spotlight and the like are required to have high energy and output characteristics, it can be seen that safety is most important.
In general, the lithium secondary battery is composed of a cathode, an anode, and an electrolyte, and lithium ions released from a cathode active material by a first charging serve to transfer energy while shuttling between both electrodes, like being inserted into an anode active material, that is, carbon particles and again being dissociated during the discharge, thereby making the charge and discharge possible.
Meanwhile, as a high-capacity battery is continuously needed for the development of mobile electronic devices, a high-capacity anode material having a much higher capacity per unit weight than carbon used as the existing anode material has been actively studied.